Why do instagram runners call structured interval workouts “fartlek”

Fartlek is just a fancy outdated term used by people who want to convey that they are knowledgeable and influential runners who deserve money for sharing there training philosophy's. A normal coach will just call it interval training or speed work

There are countless structured workouts. There's only one where you make it up, as you go, based on how you feel, the sun, wind and Earth. You're free to change the distances, paces, as you go based on how you feel. Let the fartlek stay formless, free and unstructured.

The fartlek your day to run fast and free, with your watch at home, and your instincts taking over, wind blowing in your mane like the Wild Stallion that you are.

I like doing a unique set of workouts that I coined "cruise fartleks". Sessions like: 3*10:00, 5*6:00, 6*5:00, and 10*3:00 @ Mp--> 10k pace with 45-90 second easy/moderate jog depending on if I'm at altitude camp.

So you just made that up??

Let's be honest , most of the terminology used to describe training today is either just plain wrong or is the result of coaches trying to make believe they've invented something that they have not. When a progression run becomes a "snowball", "cut downs" or "acceleration run" that's just confusing jargon. When a true "speed play" suddenly becomes a "structured fartlek" you're just wrong. That's an interval workout. There is no difference between a 1-2-3-2-1 "fartlek" and 400-600-800-600-400 with equal intervals. As much as I respect my former travel roommate Steve, "Mona fartleks" are not fartleks. One of the original objectives of Coaching Education was suppossed to be getting everyone using a common terminology.

Don't even get me started on what has happened to what used to be known as cross country......

This.

Yes, it’s technically improper usage of the word in relation to its original meaning, but it’s become the understood meaning today. So much easier than having to say “time-based intervals with continuous jogging rest”. It also typically implies less structured paces and a roaming route as opposed to doing it on the track or on a measured path.

If we limited the use of “fartlek“ to its original meaning, it would almost entirely fall out of usage given that virtually no training programs include true original fartleks today.

there is nothing that is easier or simpler than saying 5 x 3 minutes at x pace with 2 minutes jogging rest.

if people aren't actually doing fartleks, then why does the word still need to be used?

If they are almost completely out of use, by their original definition, that tells me people don't enjoy them or find them valuable. or a combination of both of those things.